#include "md5.h"
#include <string.h>

/*
 ***********************************************************************
 **  Message-digest routines:                                         **
 **  To form the message digest for a message M                       **
 **    (1) Initialize a context buffer mdContext using MD5Init        **
 **    (2) Call MD5Update on mdContext and M                          **
 **    (3) Call MD5Final on mdContext                                 **
 **  The message digest is now in mdContext.digest[0...15]           **
 ***********************************************************************
 */
static MD5_CTX mdContext;

const uint8_t MD5_PADDING[64] = {
  0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

/* F, G, H and I are basic MD5 functions */
#define F(x, y, z)	(((x) & (y)) | ((~x) & (z)))
#define G(x, y, z)	(((x) & (z)) | ((y) & (~z)))
#define H(x, y, z)	((x) ^ (y) ^ (z))
#define I(x, y, z)	((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4 */
/* Rotation is separate from addition to prevent recomputation */
#define FF(a, b, c, d, x, s, ac)	\
	{	\
		(a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac);	\
		(a) = ROTATE_LEFT ((a), (s));						\
		(a) += (b);											\
	}
#define GG(a, b, c, d, x, s, ac)	\
	{	\
		(a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac);	\
		(a) = ROTATE_LEFT ((a), (s));						\
		(a) += (b);											\
	}
#define HH(a, b, c, d, x, s, ac)	\
	{	\
		(a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac);	\
		(a) = ROTATE_LEFT ((a), (s));						\
		(a) += (b);											\
	}
#define II(a, b, c, d, x, s, ac)	\
	{	\
		(a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac);	\
		(a) = ROTATE_LEFT ((a), (s));						\
		(a) += (b);											\
	}

#define UL(x) x##UL

/**
	Basic MD5 step. Transforms buf based on in.
  */
static void Transform (uint32_t *buf, uint32_t *in)
{
	register uint32_t a = buf[0];
	register uint32_t b = buf[1];
	register uint32_t c = buf[2];
	register uint32_t d = buf[3];

	/* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
	FF ( a, b, c, d, in[ 0], S11, UL(3614090360)); /* 1 */
	FF ( d, a, b, c, in[ 1], S12, UL(3905402710)); /* 2 */
	FF ( c, d, a, b, in[ 2], S13, UL( 606105819)); /* 3 */
	FF ( b, c, d, a, in[ 3], S14, UL(3250441966)); /* 4 */
	FF ( a, b, c, d, in[ 4], S11, UL(4118548399)); /* 5 */
	FF ( d, a, b, c, in[ 5], S12, UL(1200080426)); /* 6 */
	FF ( c, d, a, b, in[ 6], S13, UL(2821735955)); /* 7 */
	FF ( b, c, d, a, in[ 7], S14, UL(4249261313)); /* 8 */
	FF ( a, b, c, d, in[ 8], S11, UL(1770035416)); /* 9 */
	FF ( d, a, b, c, in[ 9], S12, UL(2336552879)); /* 10 */
	FF ( c, d, a, b, in[10], S13, UL(4294925233)); /* 11 */
	FF ( b, c, d, a, in[11], S14, UL(2304563134)); /* 12 */
	FF ( a, b, c, d, in[12], S11, UL(1804603682)); /* 13 */
	FF ( d, a, b, c, in[13], S12, UL(4254626195)); /* 14 */
	FF ( c, d, a, b, in[14], S13, UL(2792965006)); /* 15 */
	FF ( b, c, d, a, in[15], S14, UL(1236535329)); /* 16 */

	/* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
	GG ( a, b, c, d, in[ 1], S21, UL(4129170786)); /* 17 */
	GG ( d, a, b, c, in[ 6], S22, UL(3225465664)); /* 18 */
	GG ( c, d, a, b, in[11], S23, UL( 643717713)); /* 19 */
	GG ( b, c, d, a, in[ 0], S24, UL(3921069994)); /* 20 */
	GG ( a, b, c, d, in[ 5], S21, UL(3593408605)); /* 21 */
	GG ( d, a, b, c, in[10], S22, UL(  38016083)); /* 22 */
	GG ( c, d, a, b, in[15], S23, UL(3634488961)); /* 23 */
	GG ( b, c, d, a, in[ 4], S24, UL(3889429448)); /* 24 */
	GG ( a, b, c, d, in[ 9], S21, UL( 568446438)); /* 25 */
	GG ( d, a, b, c, in[14], S22, UL(3275163606)); /* 26 */
	GG ( c, d, a, b, in[ 3], S23, UL(4107603335)); /* 27 */
	GG ( b, c, d, a, in[ 8], S24, UL(1163531501)); /* 28 */
	GG ( a, b, c, d, in[13], S21, UL(2850285829)); /* 29 */
	GG ( d, a, b, c, in[ 2], S22, UL(4243563512)); /* 30 */
	GG ( c, d, a, b, in[ 7], S23, UL(1735328473)); /* 31 */
	GG ( b, c, d, a, in[12], S24, UL(2368359562)); /* 32 */

	/* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
	HH ( a, b, c, d, in[ 5], S31, UL(4294588738)); /* 33 */
	HH ( d, a, b, c, in[ 8], S32, UL(2272392833)); /* 34 */
	HH ( c, d, a, b, in[11], S33, UL(1839030562)); /* 35 */
	HH ( b, c, d, a, in[14], S34, UL(4259657740)); /* 36 */
	HH ( a, b, c, d, in[ 1], S31, UL(2763975236)); /* 37 */
	HH ( d, a, b, c, in[ 4], S32, UL(1272893353)); /* 38 */
	HH ( c, d, a, b, in[ 7], S33, UL(4139469664)); /* 39 */
	HH ( b, c, d, a, in[10], S34, UL(3200236656)); /* 40 */
	HH ( a, b, c, d, in[13], S31, UL( 681279174)); /* 41 */
	HH ( d, a, b, c, in[ 0], S32, UL(3936430074)); /* 42 */
	HH ( c, d, a, b, in[ 3], S33, UL(3572445317)); /* 43 */
	HH ( b, c, d, a, in[ 6], S34, UL(  76029189)); /* 44 */
	HH ( a, b, c, d, in[ 9], S31, UL(3654602809)); /* 45 */
	HH ( d, a, b, c, in[12], S32, UL(3873151461)); /* 46 */
	HH ( c, d, a, b, in[15], S33, UL( 530742520)); /* 47 */
	HH ( b, c, d, a, in[ 2], S34, UL(3299628645)); /* 48 */

	/* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
	II ( a, b, c, d, in[ 0], S41, UL(4096336452)); /* 49 */
	II ( d, a, b, c, in[ 7], S42, UL(1126891415)); /* 50 */
	II ( c, d, a, b, in[14], S43, UL(2878612391)); /* 51 */
	II ( b, c, d, a, in[ 5], S44, UL(4237533241)); /* 52 */
	II ( a, b, c, d, in[12], S41, UL(1700485571)); /* 53 */
	II ( d, a, b, c, in[ 3], S42, UL(2399980690)); /* 54 */
	II ( c, d, a, b, in[10], S43, UL(4293915773)); /* 55 */
	II ( b, c, d, a, in[ 1], S44, UL(2240044497)); /* 56 */
	II ( a, b, c, d, in[ 8], S41, UL(1873313359)); /* 57 */
	II ( d, a, b, c, in[15], S42, UL(4264355552)); /* 58 */
	II ( c, d, a, b, in[ 6], S43, UL(2734768916)); /* 59 */
	II ( b, c, d, a, in[13], S44, UL(1309151649)); /* 60 */
	II ( a, b, c, d, in[ 4], S41, UL(4149444226)); /* 61 */
	II ( d, a, b, c, in[11], S42, UL(3174756917)); /* 62 */
	II ( c, d, a, b, in[ 2], S43, UL( 718787259)); /* 63 */
	II ( b, c, d, a, in[ 9], S44, UL(3951481745)); /* 64 */

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;
}

/**
	The routine MD5Init initializes the message-digest context
	mdContext. All fields are set to zero.
  */
void MD5_Init(void)
{
	mdContext.i[0] = mdContext.i[1] = 0;

	/* Load magic initialization constants. */
	mdContext.buf[0] = UL(0x10325476);
	mdContext.buf[1] = UL(0x98BADCFE);
	mdContext.buf[2] = UL(0xEFCDAB89);
	mdContext.buf[3] = UL(0x67452301);
}

/**
	The routine MD5Update updates the message-digest context to
	account for the presence of each of the characters inBuf[0..inLen-1]
	in the message whose digest is being computed.
  */
void MD5_Update(const uint8_t *inBuf, uint8_t inLen)
{
	uint32_t in[16];
	int mdi;
	unsigned int i, ii;

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext.i[0] >> 3) & 0x3F);

	/* update number of bits */
	if ((mdContext.i[0] + ((uint32_t)inLen << 3)) < mdContext.i[0])
		mdContext.i[1]++;

	mdContext.i[0] += ((uint32_t)inLen << 3);
	mdContext.i[1] += ((uint32_t)inLen >> 29);

	while (inLen--)
	{
		/* add new character to buffer, increment mdi */
		mdContext.in[mdi++] = *inBuf++;

		/* transform if necessary */
		if (mdi == 64)
		{
			for (i = 0, ii = 0; i < 16; i++, ii += 4)
			{
				in[i] = (((uint32_t)mdContext.in[ii+3]) << 24) |
						(((uint32_t)mdContext.in[ii+2]) << 16) |
						(((uint32_t)mdContext.in[ii+1]) << 8)  |
						((uint32_t)mdContext.in[ii]);
			}
			Transform (mdContext.buf, in);
			mdi = 0;
		}
	}
}

/**
	The routine MD5Final terminates the message-digest computation and
	ends with the desired message digest in mdContext->digest[0...15].
  */
void MD5_Final (uint8_t * hash)
{
	uint32_t in[16];
	int mdi;
	unsigned int i, ii;
	unsigned int padLen;

	/* save number of bits */
	in[14] = mdContext.i[0];
	in[15] = mdContext.i[1];

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext.i[0] >> 3) & 0x3F);

	/* pad out to 56 mod 64 */
	padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);
	MD5_Update (MD5_PADDING, padLen);

	/* append length in bits and transform */
	for (i = 0, ii = 0; i < 14; i++, ii += 4)
	{
		in[i] = (((uint32_t)mdContext.in[ii+3]) << 24) |
				(((uint32_t)mdContext.in[ii+2]) << 16) |
				(((uint32_t)mdContext.in[ii+1]) << 8)  |
				((uint32_t)mdContext.in[ii]);
	}
	Transform (mdContext.buf, in);

	/* store buffer in digest */
	for (i = 0, ii = 0; i < 4; i++, ii += 4)
	{
		mdContext.digest[ii]   = (uint8_t)((mdContext.buf[i] >>  0) & 0xFF);
		mdContext.digest[ii+1] = (uint8_t)((mdContext.buf[i] >>  8) & 0xFF);
		mdContext.digest[ii+2] = (uint8_t)((mdContext.buf[i] >> 16) & 0xFF);
		mdContext.digest[ii+3] = (uint8_t)((mdContext.buf[i] >> 24) & 0xFF);
	}
	memcpy(hash, mdContext.digest, 16);
}
